The invention relates to flexible seating structures for valves, e.g. rotary valves.
A rotary valve, e.g. a ball or butterfly valve, typically has a closure member which, in a first (open) position, allows fluid to pass through a valve passageway and which, in a second (closed) position, prevents fluid from flowing through the valve passageway. The closure member typically has a sealing surface, typically rounded or spherical, and flow is prevented in the second position by sealing engagement of the sealing surface of the closure member with a corresponding seating surface of the valve.
In common, everyday valves (not necessarily rotary valves), such as those present in a household water faucet, the seating surface is often provided by a soft, resilient material such as rubber or silicone. Tight contact is achieved by pressing the closure member into the soft seating material in a manner to deform the seating material to fit the contours of the closure member.
In many valve applications, however, such as where corrosive or abrasive conditions are present, it is necessary to provide a metal seating surface, which has a more limited capability to deform to fit the contours of the closure member. As a result, a high degree of precision is typically required in manufacture and assembly of valve components in order to ensure that the closure member makes continuous, sealing contact with the seating surface. Such high precision is often difficult and expensive to achieve and/or maintain. As a result, it is well recognized in the industry that metal-seated rotary valves are, in many instances, prone to leakage with poor sealing.